When I feed F/T I let the rat thaw for several hours. When it reaches room temperature, I use a blow dryer on it to heat it up. Its the same blow dryer I use on my hair, and I never had any problems. It may just be that the snake didn't want the f/t mouse. Was it the first time you attempted to feed the snake f/t? There are a lot of threads that give advice on switching snakes from live to f/t, maybe you could try some of those tricks. Good luck!